The present invention relates generally to an optical switch, and more particularly to a compact, high-speed optical switch which can reduce insertion loss and crosstalk by forming a plurality of electrodes separated in the direction of propagation of a light beam on at least one of the main surfaces of a dielectric substrate having a periodic structure of polarization inverted domains. The present invention relates also to an optical disk drive using such an optical switch to selectively access a plurality of optical disks, for example.
In optical communication, an optical switch is used to switch the optical path of a light beam. The optical switch now in use is generally classified into a mechanical type and an electronic type.
The mechanical type optical switch is so designed as to mechanically switch the optical path of a light beam. Although the mechanical type optical switch has an advantage that the insertion loss and crosstalk are sufficiently small, the switching speed is as low as 1 to 100 msec. In contrast, the electronic type optical switch is so designed as to guide a light beam by means of a waveguide formed on a dielectric substrate, for example. Although the electronic type optical switch has an advantage that the switching speed is as high as 100 xcexcsec to 10 nsec, the insertion loss is large and the crosstalk is xe2x88x9230 dB at the minimum.
In such an optical switch, it is desired both to reduce the insertion loss and crosstalk and to increase the switching speed. In this respect, the conventional mechanical type optical switch has a problem that the switching speed is low, and the conventional electronic type optical switch has a problem that the insertion loss and crosstalk are large.
In the case of switching a light beam to emerge it selectively from multiple outputs by using an optical switch having the conventional configuration, there is a problem that the configuration of the optical switch becomes large in size. As the electronic type optical switch, a bulk type optical switch is known. However, the switching speed of the bulk type optical switch is 1 to 100 xcexcsec, which is lower than that of the other type optical switch using a waveguide.
It is accordingly an object of the present invention to provide a compact, high-speed optical switch which can reduce insertion loss and crosstalk.
It is another object of the present invention to provide an optical disk drive using the optical switch.
In accordance with an aspect of the present invention, there is provided an optical switch including a dielectric substrate having a pair of main surfaces opposed to each other; and a pair of electrodes formed on the main surfaces of the dielectric substrate; wherein a direction of emergence of a light beam propagating in the dielectric substrate is controlled according to an electric field applied from the electrodes to the dielectric substrate; the dielectric substrate being formed with a periodic structure of polarization inverted domains each having a given shape; the light beam being incident on domain walls of the polarization inverted domains; the electrode formed on at least one of the main surfaces being separated into at least first and second electrodes in a direction of propagation of the light beam.
In accordance with another aspect of the present invention, there is provided an optical disk drive including a laser light source for emitting a light beam; and an optical pickup for switching the optical path of the light beam emitted from the laser light source to supply the light beam selectively to a plurality of optical disks, thereby selectively accessing the plurality of optical disks, wherein the optical pickup is configured by using the above optical switch.
As described above, a periodic structure of polarization inverted domains each having a given shape is formed in the dielectric substrate, so that the light beam incident on the domain walls of the polarization inverted domains undergoes Bragg diffraction due to the periodic structure of polarization inverted domains to cause emergence of the light beam in a given direction or distribution of the light beam. Further, since the electrodes are formed on the main surfaces of the dielectric substrate, the direction of emergence of the light beam propagating in the dielectric substrate can be controlled according to an electric field applied from the electrodes to the dielectric substrate. Accordingly, it is possible to obtain an optical switch which can reduce insertion loss and crosstalk and can achieve a high switching speed. Further, the electrode formed on at least one of the main surfaces is separated into at least first and second electrodes in a direction of propagation of the light beam. Accordingly, it is possible to obtain a compact optical switch having multiple outputs corresponding to the first and second electrodes.
Other objects and features of the invention will be more fully understood from the following detailed description and appended claims when taken with the accompanying drawings.